Alcohol elicits unique cardiovascular responses, which are not only dependent on the neuronal substrates within the brainstem but also on the genetic state of these neurons. The objective of this proposal is to elucidate the molecular mechanisms implicated in the differential effect of ethanol on specialized neurons in the brainstem that control blood pressure and cardiac reflexes in a model of essential hypertension, the spontaneously hypertensive rat (SHR). Our recent intriguing findings showed that site dependent neurochemical (norepinephrine, NE) and IEG gene/protein expression (c-jun/c-Jun) responses elicited by ethanol in the ventrolateral medulla (RVLM) and nucleus tractus solitarius (NTS) determine its divergent effects on blood pressure and baroreflex responses in hypertensive and normotensive rats. Given the altered cardiovascular neurobiology and neuronal sensitivity to ethanol in SHRs, we hypothesize that heme oxygenase (HO) derived carbon monoxide (CO) constitutes a novel molecular mechanism for the centra! cardiovascular effects of ethanol. To test this hypothesis, we propose a series of integrative, and molecular studies under three aims. Aim 1 establishes brainstem HO-CO pathway as a molecular mechanism for the divergent cardiovascular actions of ethanol in SHRs and WKY rats. Aim 2 will elucidate the effect of ethanol on the association of HO with its regulatory proteins caveolin-1 and calmodulin in brainstem neurons of SHRs and WKY rats. Aim 3 characterizes the role of HO-CO-MAPK pathway in ethanol-mediated cardiovascular responses. Since catalase activity (the major enzyme that metabolizes ethanol in the brain) is altered in SHRs, the potential contribution of acetaldehyde to ethanol actions will be investigated. The proposal adopts a well designed experimental approach that incorporates an established model system, appropriate controls and pharmacological and siRNA interventions to: (i) establish a causal relationship between inhibition of HO-derived CO and the sympathoexcitatory (pressor) and baroreflex depressant effects of ethanol, and (ii) identify the molecular mechanisms implicated in the site- and strain-dependent neurochemical and cardiovascular effects of ethanol. The proposed research whose primary focus is to probe the molecular mechanisms implicated in the adverse ethanol effects on cardiovascular neurobiology, addresses a significant biomedical problem and is expected to yield clinically relevant information.